Phenol biodegradation by immobilized Rhodococcus qingshengii isolated from coking effluent on Na-alginate and magnetic chitosan-alginate nanocomposite

Reusable magnetic alginate nanocomposite with immobilized Pseudozyma antarctica yeast cells offers the potential for bioremediation and detoxification of reactive black 5 dye

Azo dyes in wastewater of textile, paper and pulp, cosmetics, and leather tanning industries have toxicity and mutagenicity for all living organisms. The aim of the current research was the study of free and immobilized yeast cells of Pseudozyma antarctica on the beads of magnetic alginate nanocomposite to decolorize and detoxify Reactive Black 5 (RB5) as a representative of azo dyes. This yeast decolorized a high concentration of RB5 (2500 mg/L) with 82.30 % decolorization efficiency. The beads containing immobilized yeast cells were used for decolorization in consecutive cycles, and the decolorization efficiency of the beads after four cycles was more than 67 %. UV-visible and FTIR spectroscopy studies showed that the azo bond in RB5 was removed and destroyed by yeast activity. The azo bond of RB5 is destroyed in the biodegradation mechanism which confirms the decolorization of RB5 by P. antarctica via the biodegradation mechanism. According to the phytotoxicity results, RB5 decolorization by P. antarctica reduced the toxicity of the dye. This is the first study on the decolorizing and detoxifying potentials of P. antarctica and introduces a promising candidate for the treatment of wastewater containing azo dyes. Furthermore, its successful immobilization on magnetic alginate nanocomposite and its convenient consecutive uses make it more attractive for environmental applications.

Recent advances in the nitrogen cycle involving actinomycetes: Current situation, prospect and challenge

Actinomycetes are essential for sustaining the ecosystem's nitrogen balance and stimulating plant development. In contrast, existing detection and culture techniques for actinomycetes are still limited, making it difficult to fully assess their role in the nitrogen cycle. This review emphasized the advantages of actinomycetes in ecological restoration, outlined the current status and challenges of research on nitrogen cycling by actinomycetes. Special attention was paid to the metabolic pathways and related gene regulatory mechanisms of nitrogen fixation, nitrification, denitrification, dissimilatory nitrate reduction to ammonium, and ammonium assimilation processes. The limitations and strategies of actinomycetes nitrogen metabolic pathways were revealed. In addition, the involvement of carbon, sulphur and phosphorus in the nitrogen cycle of actinomycetes was pointed out. The aim of the review is to improve our understanding of the function of actinomycetes in the nitrogen cycle, which is crucial for enhancing wastewater treatment, ecological preservation, and agricultural output.

Integrated biological-chemical system for phenol removal from petrochemicals wastewater

Phenol is a highly concerning pollutant in petrochemical industrial wastewater. It is extremely poisonous, carcinogenic, and persistent, therefore, it bioaccumulates in the food chain reaching humans, where it causes acute irritation to the skin, eyes, and respiratory tract, as well as chronic effects on the liver, kidneys, and nervous system. It spills or leaks easily into surface water or groundwater sources, leading to the creation of other harmful substituted compounds. Therefore, the present study aimed to design an integrated biological-chemical system (phenol degrader(s) and nanoparticle assemblage) for the efficient removal of phenolic compounds from wastewater of a poly-vinyl chloride production unit at a petrochemical company in Alexandria. Ten indigenous microbial isolates were obtained from phenol-contaminated wastewater and purified. Two fungal isolates were excluded, and eight bacterial isolates were screened for their efficiency in the degradation and removal of phenol. Three isolates (Stutzerimonas chloritidismutans strain AW-1 (A2), Stutzerimonas stutzeri ATCC 17588 = LMG 11199 (A4), and Arthrobacter ruber strain MDB1-42 (A9)) proved to be the most promising candidate(s) and were investigated as individual and mixed cultures. The mixed culture (A2, A4, and A9) proved to be the most efficient, and could achieve 98.85, 31.08, 45.83, and 45.83% removal of phenol, chemical oxygen demand (COD), biochemical oxygen demand (BOD), and total dissolved solids (TDS), respectively (all below their maximum permissible limits (MPLs)), for discharge or reuse. The bacterial consortium was decorated with the synthesized and characterized Fe3O4 Nanoparticles (NPs) at 1:3 (g/g), the optimum ratio for coating and immobilization (94.22%) of the bacterial consortium. Fe3O4 NP/bacteria assembly (trial 1) showed the highest RE of 20, 56.66, 47.06, 25.16, and 96.78% for TDS, total suspended solids (TSS), BOD, COD, and phenol, respectively, all after only 1 h except TSS (2 h), compared to the treatment with undecorated bacterial consortium (trial 2) or bacteria-free Fe3O4 NPs (trial 3). It is concluded that the proposed treatment system (Fe3O4 NP/bacterial assembly) is an extraordinarily effective, practical, quick, clean, renewable, long-lasting, ecologically friendly, and simply implemented technology for remediating phenol-contaminated wastewater compared to other conventional treatment methods. Concerning TSS, COD, and phenol residues that are still higher than their MPLs, it can be easily overcome by increasing the exposure (contact) time or the dose of the Fe3O4 NP/bacterial assembly, using multiple units of the proposed treatment in sequence, or fixing the decorated bacteria as a biofilm system and treating the effluent in a continuous mode.

Phenol biodegradation using bio-filter tower packed column with immobilized bacterial consortium: a batch test study

The effluents from pulp and paper manufacturing industries contain high concentrations of phenol, which when discharged directly into surface water streams, increases the biological oxygen demand (BOD) and chemical oxygen demand (COD). In this study, two dominant bacteria SP-4 and SP-8 were isolated from the effluent emanating with a pulp and paper industry. The selected phenol-degrading isolates were identified as Staphylococcus sp. and Staphylococcus sciuri respectively by using nucleotide sequence alignment and phylogenetic analysis of 16 S rRNA regions of the genome. The two isolates used for the biodegradation process effectively degraded phenol concentration of pulp and paper industry effluent upto 1600 and 1800 mg/L resepctively. The individual isolates and consortium were immobilized using activated carbon, wood dust, and coal ash. Additionally, the effluent was treated using a bio-filter tower packed column immobilized with bacterial cells at a constant flow rate of 5 mL/min. The present study showed that the developed immobilized microbial consortium can effectively degrade 99% of the phenol present in pulp and paper industry effluents, resulting in a significant reduction in BOD and COD of the system. This study can be well implemented on real-scale systems as the bio-filter towers packed with immobilized bacterial consortium can effectively treat phenol concentrations up to 1800 mg/L. The study can be implemented for bioremediation processes in phenolic wastewater-contaminated sites.

Facilitation of coke gasification by coking wastewater and its degradation properties in thermochemical reactions

The thermochemical reaction between coking wastewater and gasification-coke is a new way to achieve efficient and clean use of coal and solve the problem of coking wastewater treatment in the Gansu Longdong region. To further investigate the thermochemical reaction characteristics of coking wastewater and gasification-coke, this paper explores the effect of coking wastewater on syngas production from coke gasification at 1000 °C, the degradation effect of organic pollutants in coking wastewater, the thermochemical reactivity of gasification-coke, and the reasons why wastewater promotes coke gasification and wastewater degradation. The results showed that the thermochemical reaction of coking wastewater with gasification-coke not only facilitates the improvement of syngas yield and low-level calorific value but also improves the thermochemical reactivity of gasification-coke. Notably, phenol in coking wastewater plays a major role in promoting the gasification of gasification-coke. During the thermochemical reaction, the organic pollutants in the wastewater were effectively degraded, the degradation rate of CODCr reached more than 85%, and the degradation of organic pollutants reached more than 75%. Phenol water and coking wastewater can not only improve the dispersion of the ash phase on the surface of gasification-coke, effectively inhibiting the sintering and agglomeration of the ash phase in gasification-coke, but also change the type and number of organic functional groups in gasification-coke. Therefore, coking wastewater can promote the gasification of coke. The thermochemical reaction between coke wastewater and gasification-coke can simultaneously promote coke gasification and the degradation of coke wastewater and achieve the resourceful use of coke wastewater.

Biodegradation of phenolic pollutants and bioaugmentation strategies: A review of current knowledge and future perspectives

The widespread use of phenolic compounds renders their occurrence in various environmental matrices, posing ecological risks especially the endocrine disruption effects. Biodegradation-based techniques are efficient and cost-effective in degrading phenolic pollutants with less production of secondary pollution. This review focuses on phenol, 4-nonylphenol, 4-nitrophenol, bisphenol A and tetrabromobisphenol A as the representatives, and summarizes the current knowledge and future perspectives of their biodegradation and the enhancement strategy of bioaugmentation. Biodegradation and isolation of degrading microorganisms were mainly investigated under oxic conditions, where phenolic pollutants are typically hydroxylated to 4-hydroxybenzoate or hydroquinone prior to ring opening. Bioaugmentation efficiencies of phenolic pollutants significantly vary under different application conditions (e.g., increased degradation by 10-95% in soil and sediment). To optimize degradation of phenolic pollutants in different matrices, the factors that influence biodegradation capacity of microorganisms and performance of bioaugmentation are discussed. The use of immobilization strategy, indigenous degrading bacteria, and highly competent exogenous bacteria are proposed to facilitate the bioaugmentation process. Further studies are suggested to illustrate 1) biodegradation of phenolic pollutants under anoxic conditions, 2) application of microbial consortia with synergistic effects for phenolic pollutant degradation, and 3) assessment on the uncertain ecological risks associated with bioaugmentation, resulting from changes in degradation pathway of phenolic pollutants and alterations in structure and function of indigenous microbial community.

Biochar inoculated with Rhodococcus biphenylivorans altered microecological regulation by promoting quorum sensing and electron transfer: Up-regulation of related genes and enhancement of phenol and ammonia degradation

Bioaugmentation is an efficient method for improving the efficiency of coking wastewater removal. Nevertheless, how different immobilization approaches affect the efficiency of bioaugmentation remains unclear, as does the corresponding mechanism. With the assistance of immobilized bioaugmentation strain Rhodococcus biphenylivorans B403, the removal of synthetic coking wastewater was investigated (drying agent, alginate agent, and absorption agent). The reactor containing the absorption agent exhibited the highest average removal efficiency of phenol (99.74 %), chemical oxygen demand (93.09 %), and NH4+-N (98.18 %). Compared to other agents, the covered extracellular polymeric substance on the absorption agent surface enhanced electron transfer and quorum sensing, and the promoted quorum sensing benefited the activated sludge stability and microbial regulation. The phytotoxicity test revealed that the wastewater's toxicity was greatly decreased in the reactor with the absorption agent, especially under high phenol concentrations. These findings showed that the absorption agent was the most suitable for wastewater treatment bioaugmentation.

Enhanced ammonia nitrogen and phenol removal by immobilized bacteria through composite mycelium pellet-driven quinone redox cycle

The composite mycelium pellet (CMP) was coupled with Pseudomonas sp. Y1 (CMP-Y1) to remove phenol and ammonia nitrogen (NH4+-N). The CMP was formed by the self-assembly of fungal mycelium with sponge iron (SIO), gallic acid (GA), and oxalic acid. The results showed that CMP with abundant pore size and successful internal loading of sponge iron containing iron nanoparticles. CMP could induce GA redox cycle to form Fenton-like reaction and thus achieve efficient phenol removal (93.32%, 24 h). Meanwhile, the removal efficiencies of phenol, NH4+-N, and chemical oxygen demand (COD) using CMP-Y1 at 12 h were 93.71, 92.40, and 89.00%, respectively. The increase in the electron transfer activity of strain Y1 by the addition of CMP could facilitate the nitrogen removal processes. In addition, high-throughput sequencing results indicated the abundance of antioxidant and repair genes was increased, which might be a strategy of strain Y1 to cope with oxidative stress. This strategy provided the possibility for the practical application of the combination of advanced oxidation and biological treatment, and offered new insights into the symbiotic system of fungi and bacteria.

Dual metabolic pathways co-determine the efficient aerobic biodegradation of phenol in Cupriavidus nantongensis X1

Phenol, as an important chemical raw material, often exists in wastewater from chemical plants and pollutes soil and groundwater. Aerobic biodegradation is a promising method for remediation of phenolic wastewater. In this study, degradation characteristics and mechanisms of phenol in Cupriavidus nantongensis X1 were explored. Strain X1 could completely degrade 1.5 mM phenol within 32 h and use it as the sole carbon source for growth. The optimal degradation temperature and pH for phenol by strain X1 were 30 °C and 7.0. The detection of 3-oxoadipate and 4-hydroxy-2-oxopentanoate indicated that dual metabolic pathways coexist in strain X1 for phenol degradation, ortho- and meta-pathway. Genome and transcriptome sequencing revealed the whole gene clusters for phenol biomineralization, in which C12O and C23O were key enzymes in two metabolic pathways. The ribosome proteins were also involved in the regulation of phenol degradation. Meanwhile, the degradation activities of enzyme C23O was 188-fold higher than that of C12O in vitro, which indicated that the meta-pathway was more efficient than ortho-pathway for catechol degradation in strain X1. This study provides an efficient strain resource for phenol degradation, and the discovery of dual metabolic pathways provides new insight into the aerobic biological metabolism and bioremediation of phenol.

Foliar application of chitosan-putrescine nanoparticles (CTS-Put NPs) alleviates cadmium toxicity in grapevine (Vitis vinifera L.) cv. Sultana: modulation of antioxidant and photosynthetic status

BACKGROUND

Cadmium (Cd) stress displays critical damage to the plant growth and health. Uptake and accumulation of Cd in plant tissues cause detrimental effects on crop productivity and ultimately impose threats to human beings. For this reason, a quite number of attempts have been made to buffer the adverse effects or to reduce the uptake of Cd. Of those strategies, the application of functionalized nanoparticles has lately attracted increasing attention. Former reports clearly noted that putrescine (Put) displayed promising effects on alleviating different stress conditions like Cd and similarly chitosan (CTS), as well as its nano form, demonstrated parallel properties in this regard besides acting as a carrier for many loads with different applications in the agriculture industry. Herein, we, for the first time, assayed the potential effects of nano-conjugate form of Put and CTS (CTS-Put NP) on grapevine (Vitis vinifera L.) cv. Sultana suffering from Cd stress. We hypothesized that their nano conjugate combination (CTS-Put NPs) could potentially enhance Put proficiency, above all at lower doses under stress conditions via CTS as a carrier for Put. In this regard, Put (50 mg L- 1), CTS (0.5%), Put 50 mg L- 1 + CTS 0.5%" and CTS-Put NPs (0.1 and 0.5%) were applied on grapevines under Cd-stress conditions (0 and 10 mg kg- 1). The interactive effects of CTS-Put NP were investigated through a series of physiological and biochemical assays.

RESULTS

The findings of present study clearly revealed that CTS-Put NPs as optimal treatments alleviated adverse effects of Cd-stress condition by enhancing chlorophyll (chl) a, b, carotenoids, Fv/Fm, Y(II), proline, total phenolic compounds, anthocyanins, antioxidant enzymatic activities and decreasing Y (NO), leaf and root Cd content, EL, MDA and H2O2.

CONCLUSIONS

In conclusion, CTS-Put NPs could be applied as a stress protection treatment on plants under diverse heavy metal toxicity conditions to promote plant health, potentially highlighting new avenues for sustainable crop production in the agricultural sector under the threat of climate change.

Construction and performance assessment of Recirculating packed bed biofilm reactor (RPBBR) for effective biodegradation of p-cresol from wastewater

Wastewater containing excess phenolic compounds is considered a major environmental concern due to its adverse impacts on the ecosystem. In this work, an effort has been given to treat the p-cresol from wastewater using Recirculating Packed Bed Biofilm Reactor (RPBBR). The process parameters, namely inoculum dose, pH, and NaCl (w/v) concentration were optimized to enhance the specific growth and obtained to be 14 ml, 7.0, and 1% NaCl (w/100 ml), respectively. Maximum p-cresol removal efficiency of 99.36±0.2% was achieved at 100 mg L^-1 of p-cresol. First-order rate constants were found to be 0.70 day^-1 and 0.96 day^-1 for batch and continuous mode, respectively. The intermediates were analysed using FT-IR and GC-MS analysis. Pseudomonas fluorescens was used to assess bacterial toxicity and observed that the toxicity was reduced in case of treated wastewater. Finally, the performance of continuous RPBBR was better than the batch mode.

Tramates trogii biomass in carboxymethylcellulose-lignin composite beads for adsorption and biodegradation of bisphenol A

Tramates trogii biomass was immobilized in carboxymethyl cellulose-lignin composite beads via cross-linking with Fe(III) ions (i.e., Fe(III)-CMC@Lig(1-4)@FB). The composite beads formulations were used for the adsorption and degradation of bisphenol A (BPA) using the free fungal biomass as a control system. The maximum adsorption capacity of the free fungal biomass and Fe(III)-CMC@Lig-3@FB for BPA was found to be 57.8 and 95.6, mg/g, respectively. The degradation rates of BPA were found to be 87.8 and 89.6% for the free fungal biomass and Fe(III)CMC@Lig-3@FB for 72 h in a batch reactor, respectively. Adsorption of BPA on the free fungal biomass and Fe(III)CMC@Lig-3@FB fungal preparations described by the Langmuir and Temkin isotherm models, and the pseudo-second-order kinetic model. The values of Gibbs free energy of adsorption (ΔG°) were - 20.7 and - 25.8 kJ/mol at 298 K for BPA on the free fungal biomass and Fe(III)-CMC@Lig-3@FB beads, respectively. Moreover, the toxicities of the BPA and degradation products were evaluated with three different test organisms: (i) a freshwater micro-crustacean (Daphnia magna), (ii) a freshwater algae (Chlamydomonas reinhardti), and (iii) a Turkish winter wheat seed (Triticum aestivum L.). After treatment with the Fe(III)CMC@Lig-3@FB formulation, the degradation products had not any significant toxic effect compared to pure BPA. This work shows that the prepared composite bioactive system had a high potential for degradation of BPA from an aqueous medium without producing toxic end-products. Thus, it could be a good candidate for environmentally safe biological methods.

The use of immobilised bacteria cross-linked within magnetic alginate beads enhances the treatment of benzophenone-type UV filter chemicals by the SBR system

Benzophenone-n compounds (BPs) are applied in a broad spectrum of commercial products, one of which is sunscreen. These chemicals are frequently detected in a variety of environmental matrices worldwide, especially water bodies. BPs are defined as emerging contaminants as well as endocrine-disrupting contaminants; thus, it has become necessary to develop aggressive and green treatments to remove BPs. In this study, we used immobilised BP-biodegrading bacteria linked to reusable magnetic alginate beads (MABs). The MABs were added to a sequencing batch reactor (SBR) system to enhance the removal of 2,4-dihydroxybenzophenone (BP-1) and oxybenzone (BP-3) from sewage. The BP-1 and BP-3 biodegrading bacteria in the MABs consisted of strains from up to three genera to allow for efficient biodegradation. The strains used were Pseudomonas spp., Gordonia sp., and Rhodococcus sp. The optimal composition of the MABs consisted of 3% (w/v) alginate and 10% (w/v) magnetite. The MABs resulted in 60.8%-81.7% recovery by weight after 28 days, and there was a continuous release of bacteria. Moreover, the biological treatment of the BPs sewage improved after adding 100 g of BP1-MABs (1:27) and also 100 g BP3-MABs (1:27) into the SBR system at a hydraulic retention time (HRT) of 8 h. Compared with the SBR system without MABs, the removal rates of BP-1 and BP-3 increased from 64.2% to 71.5% and from 78.1% to 84.1%, respectively. Furthermore, the COD removal increased from 36.1% to 42.1%, and total nitrogen increased from 30.5% to 33.2%. Total phosphorus remained constant at 29%. The bacterial community analysis showed that the Pseudomonas population was <2% before the MAB addition, but increased to 56.1% by day 14. In contrast, the Gordonia sp. And Rhodococcus sp. Populations (<2%) remained unchanged throughout the 14-day treatment period.

Alginate Based Core-Shell Capsules Production through Coextrusion Methods: Recent Applications

Encapsulation is used in various industries to protect active molecules and control the release of the encapsulated materials. One of the structures that can be obtained using coextrusion encapsulation methods is the core-shell capsule. This review focuses on coextrusion encapsulation applications for the preservation of oils and essential oils, probiotics, and other bioactives. This technology isolates actives from the external environment, enhances their stability, and allows their controlled release. Coextrusion offers a valuable means of preserving active molecules by reducing oxidation processes, limiting the evaporation of volatile compounds, isolating some nutrients or drugs with undesired taste, or stabilizing probiotics to increase their shelf life. Being environmentally friendly, coextrusion offers significant application opportunities for the pharmaceutical, food, and agriculture sectors.

Alginate Core-Shell Capsules Production through Coextrusion Methods: Principles and Technologies

This paper provides an overview of coextrusion methods for encapsulation. Encapsulation involves the coating or entrapment of a core material such as food ingredients, enzymes, cells, or bioactives. Encapsulation can help compounds add to other matrices, stabilize compounds during storage, or enable controlled delivery. This review explores the principal l coextrusion methods available that can be used to produce core-shell capsules through the use of coaxial nozzles. Four methods for encapsulation by coextrusion are examined in detail, including dripping, jet cutting, centrifugal, and electrohydrodynamic systems. The targeted capsule size determines the appropriate parameters for each method. Coextrusion technology is a promising encapsulation technique able to generate core-shell capsules in a controlled manner, which can be applied to cosmetic, food, pharmaceutical, agriculture, and textile industries. Coextrusion is an excellent way to preserve active molecules and present a significant economic interest.

Rhodococcus Strains from the Specialized Collection of Alkanotrophs for Biodegradation of Aromatic Compounds

The ability to degrade aromatic hydrocarbons, including (i) benzene, toluene, o-xylene, naphthalene, anthracene, phenanthrene, benzo[a]anthracene, and benzo[a]pyrene; (ii) polar substituted derivatives of benzene, including phenol and aniline; (iii) N-heterocyclic compounds, including pyridine; 2-, 3-, and 4-picolines; 2- and 6-lutidine; 2- and 4-hydroxypyridines; (iv) derivatives of aromatic acids, including coumarin, of 133 Rhodococcus strains from the Regional Specialized Collection of Alkanotrophic Microorganisms was demonstrated. The minimal inhibitory concentrations of these aromatic compounds for Rhodococcus varied in a wide range from 0.2 up to 50.0 mM. o-Xylene and polycyclic aromatic hydrocarbons (PAHs) were the less-toxic and preferred aromatic growth substrates. Rhodococcus bacteria introduced into the PAH-contaminated model soil resulted in a 43% removal of PAHs at an initial concentration 1 g/kg within 213 days, which was three times higher than that in the control soil. As a result of the analysis of biodegradation genes, metabolic pathways for aromatic hydrocarbons, phenol, and nitrogen-containing aromatic compounds in Rhodococcus, proceeding through the formation of catechol as a key metabolite with its following ortho-cleavage or via the hydrogenation of aromatic rings, were verified.

Magnetic reed biochar materials as adsorbents for aqueous copper and phenol removal

Organics and heavy metals are common pollutants in many wastewaters and water bodies. Adsorption processes by magnetic materials can rapidly remove these pollutants from water and effectively recycle adsorbent. In this study, magnetic analyzer, X-ray diffraction, Flourier transform infrared spectroscopy, and granulometry were used to characterize the synthesized magnetic reed biochar materials (ZnFe₂O₄/biochar). Influences of adsorption time, pH, temperature, initial solution concentration, and adsorption equilibrium concentration on adsorption performances were investigated for Cu²⁺ and phenol adsorption by ZnFe₂O₄/biochar. Adsorption kinetic and isotherm models were used to describe the adsorption processes. Adsorption of phenol and Cu²⁺ by ZnFe₂O₄/biochar reached saturation within 45 min and increased slightly with the increase of temperature from 15 to 45 °C. Adsorption of Cu²⁺ increased with the increase of pH, while the adsorption of phenol peaked at pH = 6. The adsorption processes fit the pseudo-second order kinetics model, and both conformed to the Langmuir model. The fitting results show that the maximum single-component adsorption capacity of phenol and Cu²⁺ by ZnFe₂O₄/biochar is 63.29 and 12.20 mg/g, and the maximum bi-component adsorption capacity reaches 40.16 and 9.48 mg/g, respectively. All the findings demonstrate that ZnFe₂O₄/biochar has good adsorption performance for phenol and Cu²⁺.

Kinetics investigation of phenolic pollutant degradation via Serratia marcescens ABHI 001 and its application in wastewater treatment

In the present work, kinetic study has been conducted in order to effectively eliminate the p-cresol from wastewater employing isolated bacterial strain Serratia marcescens ABHI001 under batch shake flasks in the concentration varying from 50 to 500 mg/L. Further, effects of various parameters including p-cresol concentration, inoculum dosage, temperature, pH and agitation have been investigated. It was found that 10% v/v inoculum of 24 h age, was effective in degrading p-cresol. Beside this, it was noticed that the concentration of P-cresol above 100 mg/L exhibited an inhibitory effect. The maximum specific growth rate (μmax) was obtained to be 0.360 h-1 for 100 mgL-1 concentration. Further, the experimental results were well fitted with Halden's and Andrew's models and kinetic parameters μmax, KS and Ki in case of Haldane model were calculated to be 0.9697 h-1, 88.07 mgL-1 and 219.9 mgL-1, respectively whereas the corresponding values in case of Andrews's constants were 0.6917 h-1, 62.83 mgL-1 and 307.4 mgL-1, respectively. The yield coefficient for the growth on p-cresol was found to be 0.82.

Rhodococcus: A promising genus of actinomycetes for the bioremediation of organic and inorganic contaminants

Rhodococcus is a genus of actinomycetes that has been explored by the scientific community for different purposes, especially for bioremediation uses. However, the mechanisms governing Rhodococcus-mediated bioremediation processes are far from being fully elucidated. In this sense, this work aimed to compile the recent advances in the use of Rhodococcus for the bioremediation of organic and inorganic contaminants present in different environmental compartments. We reviewed the bioremediation capacity and mechanisms of Rhodococcus spp. in the treatment of polycyclic aromatic hydrocarbons, phenolic substances, emerging contaminants, heavy metals, and dyes given their human health risks and environmental concern. Different bioremediation techniques were discussed, including experimental conditions, treatment efficiencies, mechanisms, and degradation pathways. The use of Rhodococcus strains in the bioremediation of several compounds is a promising approach due to their features, primarily the presence of appropriate enzyme systems, which result in high decontamination efficiencies; but that vary according to experimental conditions. Besides, the genus Rhodococcus contains a small number of opportunistic species and pathogens, representing an advantage from the point of view of safety. Advances in analytical detection techniques and Molecular Biology have been collaborating to improve the understanding of the mechanisms and pathways involved in bioremediation processes. In the context of using Rhodococcus spp. as bioremediation agents, there is a need for more studies that 1) evaluate the role of these actinomycetes on a pilot and field scale; 2) use genetic engineering tools and consortia with other microorganisms to improve the bioremediation efficiency; and 3) isolate new Rhodococcus strains from environments with extreme and/or contaminated conditions aiming to explore their adaptive capabilities for bioremediation purposes.

Biodegradation of phenol by Candida tropicalis sp.: Kinetics, identification of putative genes and reconstruction of catabolic pathways by genomic and transcriptomic characteristics

Candida tropicalis sp. was isolated with predominant biodegradation capability to phenol compounds, even with high concentration or in acid environment. The biodegradation of phenol was evaluated at the following concentrations 10-1750 mg L^-1, the strain exhibited well biodegradation efficiency. The maximum specific growth rate was 0.660 h^-1 and the specific biodegradation rates was 0.47 mg (phenol) [(mg (VSS) h]^-1. Differentially expressed genes were screened out, and results revealed a complete process of energy and carbon metabolism. The genes' arrangements and phylogenetic information showed the unique genetic characteristics of the strain. Catabolic pathways were reconstructed and some key phenol-degrading genes were obviously upregulated, including pheA, catA, OXCT and fadA. A notable detail that CMBL encoding carboxymethylenebutenolidase was speculated to be involved in a shortened pathway of phenol biodegradation, thereby contributing to the reconstruction of the novel phenol catabolic pathway through the hydrolases of dienelactone. Finally, key enzymes were verified by the analysis of specific activity.

Use of Biochar Prepared from the Açaí Seed as Adsorbent for the Uptake of Catechol from Synthetic Effluents

This work proposes a facile methodology for producing porous biochar material (ABC) from açaí kernel residue, produced by chemical impregnation with ZnCl2 (1:1) and pyrolysis at 650.0 °C. The characterization was achieved using several techniques, and the biochar material was employed as an adsorbent to remove catechol. The results show that ABC carbon has hydrophilic properties. The specific surface area and total pore volume are 1315 m2·g−1 and 0.7038 cm3·g−1, respectively. FTIR revealed the presence of oxygenated groups, which can influence catechol adsorption. The TGA/DTG indicated that the sample is thermally stable even at 580 °C. Adsorption studies showed that equilibrium was achieved in <50 min and the Avrami kinetic model best fits the experimental data, while Freundlich was observed to be the best-fitted isotherm model. Catechol adsorption on ABC biochar is governed by van der Waals forces and microporous and mesoporous filling mechanisms. The Qmax is 339.5 mg·g−1 (40 °C) with 98.36% removal of simulated effluent, showing that açaí kernel is excellent biomass to prepare good biochar that can be efficiently used to treat real industrial effluents.